FedEx has cancelled all December flights for its MD-11 cargo jets as federally mandated inspections following a recent crash are expected to take longer than anticipated, reports New York's FreightWaves.

The move comes after the deadly crash of UPS Flight 2976 in Louisville, Kentucky, which prompted the Federal Aviation Administration to ground all MD-11s until thorough inspections and repairs are completed. The National Transportation Safety Board said fatigue cracks were found in a structural section holding an engine to the left wing.

FedEx operated 28 MD-11s at the start of November, representing about eight per cent of its main line capacity. Pilots will be paid for December assignments, but the pay structure for January remains unclear. The union has opposed management's plan to place MD-11 pilots on reserve duty without defined flying requirements.

UPS has also acknowledged its MD-11 fleet will remain grounded for several months, with 277 pilots pay protected. UPS Airlines president Bill Moore told staff that more extensive inspections, including removal of engines and pylons, may be required.

Western Global Airlines has furloughed about 75 MD-11 pilots after Boeing indicated inspections could extend beyond this year. FedEx and UPS have contracted partner airlines to cover part of their schedules, though the extended grounding is expected to be costly.

FedEx spokeswoman Isabel Rollison said safety is the company's highest priority and it is working with Boeing and the FAA to return the